The present invention relates generally to rail vehicle air brakes and more specifically, to a fluid operated parking brake therefore.
The brakes for railroad vehicles are pneumatic operated brakes, or air brakes which include a brake cylinder to operate the brake shoes to engage the wheel and brake the car. The brake cylinder receives a pneumatic signal to apply the brakes and generally has a spring return. Other brake cylinders may be spring applied and air released. Most railroad cars also include a parking or hand brake, which is a manually operated device which applies the brake manually. For truck mounted brake riggings, the hand brake is generally applied to the output of the brake cylinder and more specifically to the levers which connect the brake cylinder to the brake beams. A typical example is shown in U.S. Pat. No. 5,069,312. Chains are generally connected to the levers and to a convenient place on the car to allow the manual application of the parking brake. Another example of a truck mounted brake includes brake cables which are actuated manually and remotely and are connected to the piston of the brake cylinder to manually operate the brake cylinder. A typical example is shown in U.S. Pat. No. 4,653,812 and similarly illustrated in FIGS. 1 and 2 to be assessed below. Another mechanical system for a hand brake at the output of the brake cylinder is illustrated in U.S. Pat. No. 4,019,426.
The integration of the air brake control of the brake cylinder and a manual, pneumatic and/or electropneumatic controlled parking brake is illustrated in U.S. Pat. No. 5,73 8,416. In one embodiment illustrated in FIGS. 7 and 8, the piston rod of the modified brake cylinder includes a recess to receive a latching detent controlled by a piston rod of a latching cylinder. This mechanism latches the brake in the applied position and requires a release signal to remove the detent. Thus, in even normal braking conditions, the detent is actuated.
Manual pumps to actuate separate hydraulic parking brakes on railroad vehicles are illustrated in U.S. Pat. No. 5,701,975. The parking brakes are connected to the brake beams and are independent of the normal brake cylinder.
The present invention is a fluid parking brake for a rail vehicle having a brake cylinder with a first piston responsive to fluid signals to apply and release the brakes on the vehicle. The parking brake includes a housing having a second piston in the housing and which is coupled to the first piston. An apply port in the housing receives a pressure signal to move the second piston to an apply position. A locking clutch is provided for locking the second piston at least in the applied position.
The locking clutch may have a first clutch surface carried by the housing and a second clutch surface carried by the second piston. The first and second clutch surfaces are concentric when engaged to lock the second piston and move relative to each other in either direction to disengage and unlock the second piston. The first and second clutch surfaces move relative to each other in a first direction to disengage when the second piston is in the applied position and move relative to each other in a second direction opposite the first direction to disengage when the second piston is in a released position.
The locking clutch may have a first clutch surface carried by the housing and a second clutch surface carried by the second piston. The first and second clutch surfaces are concentric when engaged to lock the second piston and move relative to each other in either directions to disengage and unlock the second piston. The first and second clutch surfaces move relative to each other in a first direction to disengage when the second piston is in the applied position and move relative to each other in a second direction opposite the first direction to disengage when the second piston is in a released position.
The first clutch surface may be on a nut threadably received on the second piston and the second clutch surface may be on a sleeve rotationally fixed to the second piston. The sleeve moves axially on the second piston. The second piston and the sleeve include opposed axial grooves and a pin in the grooves rotationally fixing the sleeve to the second piston and allowing axial movement between the sleeve and the second piston. A thrust bearing is between the nut and the housing. A spring is between the sleeve and the housing. The second piston is coupled to the first piston by a lost motion device.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.